From: Oliver Neukum <oliver@neukum.org>
Organization: NOvell
To: Greg KH <greg@kroah.com>
Subject: Re: [PATCH] USB: add USB test and measurement class driver
Date: Wed, 27 Aug 2008 10:08:24 +0200
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Cc: linux-usb@vger.kernel.org, Stefan Kopp <stefan_kopp@agilent.com>,
       Marcel Janssen <korgull@home.nl>, Felipe Balbi <me@felipebalbi.com>,
       linux-kernel@vger.kernel.org
References: <20080827000501.GA29570@kroah.com>
In-Reply-To: <20080827000501.GA29570@kroah.com>
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Am Mittwoch 27 August 2008 02:05:01 schrieb Greg KH:
> +???????intf = usb_find_interface(&usbtmc_driver, iminor(inode));
> +???????if (!intf) {
> +???????????????printk(KERN_ERR KBUILD_MODNAME
> +??????????????? ? ? ? ": can not find device for minor %d", iminor(inode));
> +???????????????return -ENODEV;
> +???????}
> +
> +???????data = usb_get_intfdata(intf);
> +???????kref_get(&data->kref);
> +
> +???????/* Store pointer in file structure's private data field */
> +???????filp->private_data = data;
> +
> +???????dev = &data->intf->dev;

> +static void usbtmc_delete(struct kref *kref)
> +{
> +       struct usbtmc_device_data *data = to_usbtmc_data(kref);
> +
> +       usb_put_dev(data->usb_dev);
> +       kfree(data->buffer);
> +       kfree(data);
> +}
> +

This is a race condition.

CPU A					CPU B
open()
usb_find_interface()
						disconnect()
						kref_put()
						usbtmc_delete()
						kfree()
kref_get()

You can write to free memory. You must use a static mutex for
mutual exclusion between open() and disconnect()

	Regards
		Oliver

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